Acoustic devices



May 1, 1962 R. E. HAMSON ACOUSTIC DEVICES Filed Feb. 2, 1960 iil INVENTOR. P0652 E. //,4M50/Y United States Patent 3,032,615 ACOUSTIC DEVICES Roger E. Hamson, Stratford, N.J., assignor to Radio Corporation of America, a corporation of Delaware Filed Feb. 2, 1960, Ser. No. 6,250 8 Claims. (Cl. 179-1155) The present invention relates to acoustic devices and methods of making the same, and more particularly to an improved arrangement for providing electrical connections to loudspeakers and microphones and to an improved method of constructing loudspeakers and microphones so as to provide the aforesaid arrangement.

Loudspeakers and some microphones of conventional design have a voice coil constituted of a plurality of turns of fine wire wound on a cylindrical coil form. The voice coil vibrates vigorously when audio signals are applied thereto. Wires are connected to the coil for the purpose of carrying audio signal currents. These wires, generally designated as lead-in wires, are subject to considerable vibration. The lead-in wires sometimes strike either the loudspeaker diaphragm or the voice coil suspension and cause objectionable buzzing. It is ordinarily the practice to use, for the lead-in wires, a type of wire which is'of heavier gauge than the wire which constitutes the voice coil winding, since the relatively fine, thin wire of the voice coil Winding is more likely to cause buzzing than heavier wires and is prone to break due to vibration produced by fatigue failure.

In miniature loudspeakers and loudspeakers of rela tively short front to back depth, it often is not feasible to use heavy gauge, relatively thick lead-in wire, since the clearance between the diaphragm and other elements in the region of the voice coil is insufficient to accommodate a heavy gauge wire. It is desirable to use part of the wire of the voice coil to constitute the lead-in wires in a manner to prevent buzzing and eliminate fatigue failure.

Conventional arrangements of lead-in wires sometimes limit the maximum audio signal power which should be applied to drive a loudspeaker. The lead-in wires may strike the diaphragm or suspension for the voice coil and cause objectional buzzing when high power audio signals are used to drive the loudspeaker.

It is an object of the present invention to provide an improved arrangement for attaching lead-in wires in electrodynamic acoustic devices and to a method of making acoustic devices so as to incorporate such an arrangement.

It is a further object of the present invention to provide improved loudspeaker and microphones wherein the wire constituting the voice coil winding may be used as a leadin connection to the voice coil.

It is a still further object of the invention to provide an improved loudspeaker with increased power handling capabilities as compared to conventional loudspeakers.

Another object of the present invention is to provide an improved loudspeaker in which the lead-in conductors are not clamped rigidly, and are damped along their full lengths whereby buzzing of the lead-in wires is avoided.

Still another object of the present invention is to provide, in a loudspeaker structure, an improved voice coil lead-in support which, while not limited thereto, is particularly useful in loudspeakers of the shallow, miniature variety.

It is also an object of the present invention to provide an improved loudspeaker of the type set forth in which the possibility of breakage of the voice coil lead-in wires is reduced to a minimum.

The improvements provided by the invention may be utilized in a loudspeaker having a vibratile diaphragm, a voice coil attached to the diaphragm and a centering, suspension member attached to the voice coil. Lead-in wires from the voice coil are disposed to extend over the suspension member. A deposit of semi-solid, elastic material, such as a gel, is disposed on the suspension memher. A material which does not dry out and maintains its shape and elasticity at temperatures somewhat exceeding room temperatures is desirable. A particularly suitable material is silicone grease. The lead-in wires are embedded in the material. so that the material substantially eliminates excessive vibration of the wires along their entire lengths. Breakage of the Wires due to vibration induced by fatigue failure and movement of the wire against the diaphragm, which causes buzzing, is therefore eliminated.

The invention itself, both as to its organization and method of operation, as well as the foregoing and other objects and advantages thereof, will become more readily apparent from a reading of the following description in connection with the accompanying drawing, in which:

FIGURE 1 is a front view, partially in section, of a loudspeaker incorporating the improvements provided by the present invention;

FIGURE 2 is a bottom, plan view of the loudspeakershown in FIGURE 1 with the diaphragm thereof partially broken away; and v 7 FIGURE 3 is a fragmentary, sectional view of the loudspeaker shown in FIGURES 1 and 2 taken along the line 33 in FIGURE 1.

Referring to the drawing, in FIGURE 1 there is shown a loudspeaker which includes a magnetic field structure 10. A housing 12 is attached to the field structure 10. A diaphragm 14 is suspended in the housing 12 at the outer periphery thereof. A voice coil form 16 is attached to the diaphragm. A voice coil winding 20 of a plurality of turns of fine wire is Wound around the voice coil. An annular, corrugated suspension member 18 is connected at the inner periphery thereof to the voice C011 form and at the outer periphery thereof to the housing. A terminal board 22 is secured to the housing. This terminal board has a pair of terminals 24 thereon. Lead-in wires 26 to the voice coil extend across the suspension member 18 and are connected to the terminals 24. It is desirable that these wires 26 be parts of the wire which constitutes the voice coil winding 20. However, the wires 26 may be separate wires which are connected to the ends of the wire constituting the voice coil winding 20.

Two bodies 28 and 30 (see FIGS. 2 and 3) of material are deposited on the suspension member 18 and the housing 12 so as to surround the lead-in wires 26, Wherefore the wires 26 are embedded or immersed in the material of the bodies 28 and 30. The bodies 28 and 30 are in the form of vein-like, elongated members. The material of the bodies 28 and 30 is a semi-solid substance which adheres to the suspension member 18 and to the housing 12 and holds the wires 26 next to the suspension member 18 and housing 12. The material of the bodies 28 and 30 is desirably semi-solid and elastic. This material has the properties of good damping and of not drying out. The material also desirably has the characteristics of maintaining its shape at elevated temperatures somewhat above normally encountered room temperatures. Such temperature stability is desirable since the loudspeaker may be incorporated in electronic apparatus which may generate sufficient heat to raise the temperature of the material constituting the bodies 28 and 30 above room temperature. The material of the bodies 28 and 30 also desirably has the property of maintaining its elasticity and consistency in a drying atmosphere, or even in a normal atmosphere, over a prolonged period of time. Thus, the material will not dry out. In any event, the lead-in wires 26 are damped against excessive vibration along their entire length by the members or bodies 28 and 30. The wires 26, thus, are prevented from striking the diaphragm 14 and the suspension 18. Buzzing due to vibration of the lead-in wires against the diaphragm 14 and the suspension 18 is eliminated. Moreover, since the vibration of the lead-in wires 26 is substantially damped, breaking of the wire caused by fatigue failure induced through excessive vibration is also eliminated.

A suitable material for the bodies 23 and 30 is a silicone grease or gel. Greases of this type are generally described in the text, An Introduction to the Chemistry of the Silicones, by Eugene G. Rochow (John Wiley and Sons, New York, second edition, 1951). A silicone grease which has been found especially suitable in type DC-3 produced by Dow-Corning, Inc., of Midland, Michigan. This material maintains its shape over a temperature range of from about -40 to about 300 F. and does not dry out.

In making an acoustic device such as the loudspeaker illustrated in FIGS. 1, 2 and 3, the lead-in wires 26 are extended across the suspension member 18 and secured to the terminals 24 on the terminal board 22. Filaments of a suitable material, such as the aforementioned silicone grease, are extruded so as to individually fiow around and surround the Wires 26. The silicone grease may be extruded from a pneumatic gun in the desired filamentary shape.

It will be apparent from the foregoing description that there has been provided an improved acoustic device and method of making the same, including an improved arrangement for providing lead-in connections to said device. While the invention has been described as being incorporated in a loudspeaker, as a preferred embodiment thereof, it will be appreciated that the invention may be utilized in microphones and other acoustic devices. Thus, it is desired that the foregoing be considered merely as illustrative and not in a limiting sense.

What is claimed is:

1. In an acoustic device having a diaphragm and a voice coil form secured to each other, a suspension member around said form and a voice coil Wound on said form, the improvement which comprises a deposit of semi-solid material adhering to said suspension member, and a lead-in wire to said coil embedded in said material.

2. The invention set forth in claim 1 wherein said material is a gel which retains its shape at temperatures in a range of temperatures including normally encountered room temperatures.

3. The invention set forth in claim 1 wherein said material has the property or" being elastic.

4. The invention as set forth in claim 1 wherein said material is a silicone grease.

5. In a loudspeaker having a housing, a diaphragm secured to said housing, a voice coil form attached to said diaphragm, an annular suspension member connected at the inner periphery thereof to said voice coil form and at the outer periphery thereof to said housing, and a voice coil wound on said form, the improvement com prising two bodies of material adhering to said member, said bodies being in the form of members extending from said voice coil form to said housing, and lead-in Wires connected to said voice coil and extending to said housing, each of said members having a different one of said wires embedded therein, said material having the characteristics of being elastic and semi-solid.

6. The invention as set forth in claim 5 wherein said material is a gel having the characteristics of retaining its elasticity and shape at temperatures substantially exceeding normally encountered room temperatures and in a drying atmosphere.

7. The invention set forth in claim 5 wherein said ma terial is a silicone grease.

8. The invention as set forth in claim 5 wherein said lead-in wires constitute parts of the wire from which said voice coil is wound.

References Cited in the file of this patent UNITED STATES PATENTS Publication, The Silicone Story, by G.E., July 1952, (EDS-4, pages 3-5 and 9 

